Vehicle braking systems has a master cylinder connected with wheel cylinders through hydraulic-pressure channels. When a driver operates a brake operation part, an upstream hydraulic pressure is produced in the master cylinder. This upstream hydraulic pressure is shut-off by a shut-off valve in order to not directly actuate the wheel cylinders, but a downstream hydraulic pressure is produced in a hydraulic-pressure source in addition to other physical quantities with the operation amount of the brake operation part to actuate the wheel cylinders. Such a control scheme is referred to as a brake-by-wire (BBW) scheme, and vehicle braking systems realizing such a control scheme have been proposed (see, for example, Patent Literature 1).